U.S. State Department spokesman Gonzalo Gallegos declined any comment on "intelligence-related matters" but did say, "A North Korean nuclear test would be an extremely provocative action that would draw universal condemnation from the international community. We continue to consult with friends and allies."

South Korea, responding to the report, said that it does not have proof that North Korea is preparing for a test. "I haven't heard that we have confirmed clear evidence that North Korea is pursuing a nuclear test," Unification Minister Lee Jong-seok told lawmakers at a hearing. Imminent nuclear testing by North Korea has been previously reported over the last two years, including the highly-publicized construction of an alleged observing area, but did not materialize.

Lee Yong-joon, head of the South Korean Foreign Ministry's task force on the North Korea nuclear issue, which monitors movements in North Korea in cooperation with the U.S., declined to comment directly on the report. The U.S. and South Korea "share all intelligence and evaluations" related to North Korean movements, Lee told AP.

While not addressing the issue of a possible test detonation, an article on the website of KCNA, the state news agency of North Korea, urged the U.S. to end its hostile policy toward North Korea and halt its invasion plans.

On July 4, North Korea conducted seven ballistic missile tests, which provoked international condemnation, including a unanimous United Nations Security Council resolution condemning its actions.

North Korea is believed to have enough nuclear material for 10 to 12 nuclear bombs, and has declared itself as having nuclear weapons, but has never tested one.